Electric-current indicator.



F. KRATZ.

BLEGTRIG CURRENT INDICATOR,

APELIGATEON IILED HDV. 18, 1910.

it gf, Patented Dec; 24, 1912.

UNITED STATES PATENT OFFICE. l

FRANZ KRATZ, F STUTTGART, GERMANY,\.\ASSIGNOR TO THE FIRM 0F ROBERTBOSCH, OF STUTTGART, GERMANY.

ELECTRIC-CURRENT INDISATOR.

Specification of Letters Patent.

Patented Dec. 24, 1912.

`Application filed November 1S, 1Mo. Serial Eo. 592,975.

In electrical sparking devices for auto"-v mobiles, for example, it veryoften happens that the operator forgets to cnt o' the ignition batteryupon stopping the car, and then electrcmagnet or not.

it' sometime elapses before operation-is resumed, the battery niaybeentirely 'exhausted by the continuous' flow ot' current from thebattery.

The invention consists in locating at a suitable place a buzzer of theusual type, for instance a Wagner hammer buzzer. The buzzer is connectedin. the conductor 'in which the current tlow is to be indicated, so thatthe opening and'closing of the buzzer contact does not interrupt theiiow of current in the conductor. 'l` his is accomplished by connectingthe vibrating arn'iature'which carries the movable buzzer cont-.ict inparallel with the Winding of the buzzer, so that a closed circuit alwaysexists whether the armature of the buzzer is attracted by the When thearmature is not so attracted the current flows thlough theelectromagnet'winding, and when the arn'iature is so attracted thecurrent -llows through the vibrating armature arid the buzzer contacts.In this way the incrementl of the armature periodically shunts thecurrent troni the electromagnet Winding. This special manner ofconnecting the buzzer is Aparticularly important for sparking vdevicesfor internal combustion engines, bec` use every interruption in thecontinuous su ply of the current occasions the production of a spark atthe ignition plug, which is prejudicial for the reason that the sparkwould occur when ignition is not desired.

The accompanying drawing forming a part of this specication isadiagrammatic view sho-wing the connections of the buzzer in accordancewith the invention.

A is abattery, B a spark coil of well known construction, haying aprimary winding e, and a secondary windin e2. The. buzzer C consists, asusual, of t e electromagnet m, the vibrating armature o and the'contacts p and p1.

The secondary Winding e, is connected to the spark plug g in the enginecylinder D. In the electric connections'between the battery A. and theprimary e1, is inserted a Switchs, which is closed in ordinaryoperation. The other end of the primary winding?, e, is connected to thestationary contact tcit the mechanically actuated interrupter flhe'movable contact f, of the nterrupter is fastened on a lever pressed bythe spring /tagainst the cam d driven by the engine in the usual manner.The stationary contact f is connected to a suitably grounded part, asthe engine body indicated, through the condenser Z; and the movablecont-act f1 is electrically connected throu a grouiided part vto thecontact p, of the zzei C.

The battery current passes o the en ine bodyg alternately through thewinding d ithe electtomagnet and the vibratiln armature in parallel withthe winding. T4 erefore, as longi' as the electrical 'connection fromthe battery is not interrupted, the buzzer will be in action. However,when the vibrating ar- $5 mature is not able to follow-the oscillationof current produced in the winding ofl the elec- 'troniagnet by amechanically actuated interrupter, for instance,` the buzzer will stop,which condition occurs when the number of interruptions is very great.Therefore, Wlhen the engine is running the mechanical interrupterprevents the operation of thfi buzzer. However-,if the mechanicallyactuated in.- tjcrrupter stops entirely, as at standstill of the engine,thel current flowing cbntinuously from the battery causes the buzzer.tooperiso vate. Therefore, if'the buzzer is`locted, for

instance, onthe dashboard of ali automobile,

the operator, upon leaving tlecar; will be reminded by the i peration ofthe buzzer that the battery is still in circuit. i.

Having thus described my invention,'what I claim is: 1. ln combinationw'ith an electric circuit, 105

through which current flows, a current indicator comprising a. buzzerhaving a Winding permanently connected in said circuit and a vibratonyarmature in electrical 'paralleli with the winding, and a periodicallyinter- 110.

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